The present invention relates to tool sharpening apparatuses, and more particularly, is directed to a sharpener attachment for a router or similar rotary tool.
A number of cutting tools include cutting edges that must be kept free from surface infections, such as burrs, nicks and gouges. Such cutting tools which need to be free from surface imperfections include chisels, planar blades, scrapers, knife members of planar machines and knife members ofjoiner machines. When surface imperfections are present on the cutting edge of tools used to remove wood from a work piece, the surface imperfection can gouge the wood surface, requiring additional sanding to be performed to obtain an acceptable appearance of the work piece.
It is known in the prior art to remove burrs and nicks and to sharpen a cutting edge of a cutting tool with a stone surface, such as wet stone, oil stone or bench stone. Such stones may be composed of natural stone or artificial material, such as silicon carbide or aluminum oxide and are available in a variety of grits. By repeated movement of the cutting edge of the cutting tool on the stone at the proper angle, material is abraded from the cutting edge surface. Typically, a stone having a course or medium grit size is used to remove surface imperfections from the cutting edge or to straighten the cutting edge. A stone having a relatively fine grit is typically employed to complete sharpening of the cutting edge.
The correct angle should be maintained between the tool and the abrading surface so that the edge is evenly sharpened. Typically, cutting tools, such as planes and chisel blades are manufactured with a cutting edge bevel that is formed by a 2 to 1 slope or an angle of approximately 25xc2x0. Maintaining a constant angle of the tool being sharpened with respect to the sharpening surface is very difficult, because the tool must be stroked across the stone surface while maintaining substantially constant pressure between the edge and the stone. Manual sharpening of a cutting tool by repeated stroking over an abrasive stone or other abrasive surface is very time consuming.
U.S. Pat. No. 5,944,592 to Hall et al. discloses a sharpening apparatus that includes a support block that holds a chisel at a desired angle. A pusher member is connected to the support block for applying a constant force to the chisel to urge the chisel""s tip against the abrasive surface. Manual or powered reciprocating movement of the support block affects abrasive action of the work piece tip against the abrasive surface to form the desired geometry.
U.S. Pat. No. 5,545,081 to Haffley et al. discloses an apparatus for holding a tool having a cutting edge in a predetermined abrading orientation with respect to a tool abrading apparatus. The apparatus includes an adjustment assembly that selectively advances and retracts a positioning member to position the tool into a predetermined abrading orientation. A tool retaining member selectively retains the tool in the predetermined abrading orientation.
The present invention concerns a sharpening attachment for sharpening cutting implements with a rotating bit of a rotary tool. The sharpening attachment includes a guide, a mount, and a clamp. The guide is configured to be connected to the rotary tool. The mount is connected to the guide such that the mount is laterally moveable along the guide. The clamp fastens the cutting implement to the mount in a position such that movement of the mount along the guide brings the cutting implement into contact with the rotating bit.
In one embodiment, the rotary tool is a router. In this embodiment, the sharpening attachment may include a mounting plate that facilitates attachment of the guide to the router or the guide may be adapted to be attached to a router table to which the router is attached.
In one embodiment, the guide includes a first end that is adapted for rotative connection to the sharpening tool and a second end that is adapted to be fixedly connected to the sharpening tool. In this embodiment, the second end of the guide may include a fine adjustment mechanism.
In one embodiment, the guide is a rail having a first end that is attached to a first mounting block and a second end that is attached to a second mounting block. The mounting blocks may be attached to the rotary tool. In one embodiment, the sharpening attachment includes a guard that is mountable to the sharpening tool to prevent the rotating bit of the rotary tool from causing injury.
A cutting implement is sharpened with a rotating bit of a rotary tool by clamping the cutting implement to a mount that is laterally movable along a guide. The guide is then positioned such that lateral movement of the mount along the guide brings the cutting edge of the cutting implement into contact with the rotating bit. The mount and the cutting implement are laterally moved along the guide to sharpen the cutting implement with the rotating bit.
In one embodiment the guide is connected directly to the rotary tool. The step of positioning the guide may be accomplished by rotating the guide about a first guide end which is rotatively connected to the sharpening tool and then fixing the second guide end to the sharpening tool. In one embodiment, the step of clamping the cutting implement to the mount holds the cutting implement at a desired angle with respect to the rotating bit.
The design of the present invention provides a cost-effective way to very quickly sharpen cutting implements and produce an extremely high quality cutting edge. The design of the present invention produces a cutting edge having a bevel of the desired angle, while squaring up blade edges. In addition, the sharpening attachment may be used with rotary tools that are typically available at construction sites, cabinet shops, furniture shops, home work shops and boat building sites, eliminating the need to provide a separate sharpening apparatus for sharpening cutting tools that are used at the construction site. The sharpener attachment quickly sharpens chisels and plane blades, and eliminates the need for time consuming hand sharpening. The attachment can be attached to a rotary tool in a short period of time. The limited number of parts associated with the attachment makes the sharpener very economical to produce and makes assembly and disassembly very easy. The attachment is lightweight and portable and provides both coarse and fine sharpening.
Additional features of the invention will become apparent and a fuller understanding will be obtained by reading the following detailed description in connection with the accompanying drawings.